The error happened during a proof of concept. It was on a humble Windows Server 2012, with nothing special on it regarding configurations or policies.
I don't understand why should I change privileges on the operating system just to download a pdf...

I simply downloaded the previous version and continued my proof of concept without any problems.

We experience the same "Access" error as mentioned above. Outsystems platform (on premise) 9.0.0.23, running on Windows 2012 (and MySQL). HTML2PdfConverter used is most recent version (just downloaded from forge).

I will try the solution mentioned above...
or just try to copy the installation files to the running path (c:\Program Files\Outsystems\Platform Server\running\HtmlToPdfConverter.158456810\binaries)

Still experiencing the same Acces to path error :-(, cannot get it to work. Installing a previous version does not make a difference. Copy the files directly to the directory on the server isn't working either.

Fixed it by changing the security settings/privileges on the Outsystems platform running directory.
Still think it is a bit odd that manually changing security privileges appears to be necessary anyway.

The changes in the mechanism had two goals. One was to support the growing community of customers and developers that use the OutSystems Platform in a Java/Linux environment and in those environements the executables are different ones and the extension didn't work.

The second main goal was to decrease the size of the extension and therefore reduce the footprint of the application and reduce publication times. The recent versions of wkhtml to pdf only for windows exceed 100MB of executables and dlls. This size would make impracticable the upload e republish of the application (not to mention that these were copied to all consumers increasing a lot the space taken on the harddrive).

Regarding this specifc problem today I personaly saw a case where it occured and it was because the espace had the runas settings using a user that didn't have permission to write on the filesystem. If that's the case I'd recommend that you give permission to the user or use the default OSPlatform user.

If you wish to use a version with everything included you can always customize your own extension or use one of the older versions (1.0.5 or bellow). if it suits your use case you should be fine with these older versions but the risk in using these versions that package discontinued wkhtml binaries is that you have no guarantee that they will work on more recent html because the webkit engine is also an old one.